Newsleaf Excerpts

Crows Redefine "Bird Brain" by Adapting to Humans

by Jason Neumann, Experiential Educator and Lester Peyton, Visitor Services Coordinator
From the September, October, November 2011 issue of Newsleaf

Corvus brachyrhynchos, the common or American crow, can be seen and heard in neighborhoods, natural preserves and agricultural areas throughout the Greater Cincinnati area. Crows rank among the most intelligent birds with their brain to body ratio equaling that of dolphins and nearly matching our own. Far from a “bird brain,” crows’ intelligence has allowed them to resourcefully take advantage of the human-created environments.

A crow’s diet varies from fruits to fish to carrion. Crows readily benefit from human activity and have been observed fashioning tools from metal wire to obtain food and stealing bait from fishing lines. After searching for the largest and heaviest nuts, some populations of crows have even learned to drop nuts in a traffic intersection and wait for passing cars to smash them open. The birds then swoop in to claim their prize.

Crows are natural scavengers; during the winter, they can sometimes be seen flying with shreds from road kills, which they will store in trees for later consumption. As opportunistic scavengers, crows have been hanging around places of human misery such as battlefields since the dawn of civilization. In fact, one of the most disturbing recollections of reporters who visited Hiroshima after the bombing was the plague of crows that descended upon the remains of the city.

The scavenging nature of crows has contributed to their reputation as vermin. Despite their intelligence, crows have historically been portrayed as a symbol of death, destruction and bad luck. Long considered a pest in the United States, crows have been hunted and persecuted by the millions. In the 1930s, the practice of “bombing” crow roosts was common. By using dynamite, thousands of birds could be killed with a single blast. The last crow roost bombing was in Stafford County, Kansas in 1952.

While crows do feed on agricultural crops, our accounting of their depredations is almost always exaggerated, one sided and seldom gives crows credit for the ways they are beneficial to us. According to one study from New York, only one percent of the food eaten during the seeding season was corn. In another, a single family of crows was found to consume about 40,000 grubs, caterpillars, army worms, and other agricultural pests during the nesting season.

Despite the historic slaughter of millions of birds, crows have increased their overall population due to changes humans have made in farming practices, forestry and city building. The health of the crow population becomes more evident as the nesting season comes to an end and crows begin to leave their territories and start to form communal roosts. Crow roosts can range from small scattered roosts of less than 100 to spectacularly large roosts of hundreds of thousands. Cincinnati’s crow roost has moved around over the years but currently resides in the Mt. Auburn/Mt. Adams area. In mid-winter,

Cincinnati’s crow population is estimated to be about 70,000.

In the early 1800s, as he fished along the Ohio River, John James Audubon witnessed the crows of Cincinnati flying to roost. Alexander Wilson’s vivid description of crows flying to their roost, penned some 200 years ago, aptly describes what can still be witnessed in the Cincinnati area today:

“About an hour before sunset, they are first observed flying, somewhat in Indian file, in one direction, at a short height about the tops of the trees, silent and steady, keeping the general curvature of the ground, continuing to pass sometimes till after sunset, so that the whole line of march would extend for many miles…Burns in a single line, has finely sketched it: The blackening trains of Crows to their repose.”

There are many possible explanations why crows form such large roosts in cities including Cincinnati. According to the Cornell Ornithology Lab, some possible answers may be:

• A prohibition on the discharge of firearms within city/village limits. It is conceivable that crows somehow stumbled across the fact that they could not be shot in cities because of local ordinances against shooting in town.

• Cities are warmer than rural areas. In most places, a difference of five to 10 degrees exists, sometimes referred to as a “heat bubble” over cities Because roosting is a winter phenomenon, warmer spots could be important.

• Great Horned Owl populations are typically lower in urban areas. Next to people with guns, Great Horned Owls pose the largest danger to an adult crow.

• Artificial light assists crows in watching for owls.

• Urban areas provide large trees for roosts. In many places, some of the largest trees are found in urban areas. Many trees in parks and cemeteries were protected from severe logging at the end of the last century, and are now some of the oldest trees around.

• During cold winters when all other bodies of water may be frozen, the Ohio River can be the only source of open water.

Crows rule the roost in terms of their intelligence among birds; they are even able to adapt to changing conditions – much like humans.

“If men had wings and bore black feathers, few of them would be clever enough to be crows.” –Rev. Henry Ward Beecher, mid 1800s

References:

Crow Busters. The Complete Resource for the Crow Hunter. Crow Busters. n.d. Web. http://www.crowbusters.com/index.htm

McGowan, Dr. Kevin J. Frequently Asked Questions About Crows. Cornell Lab of Ornithology. n.d. Web. http://www.birds.cornell.edu/crows/crowfaq.htm

Renfrow, Frank. “A History of the Crow Roost at Cincinnati.” The Ohio Cardinal. Vol. 24, No.2: Pages 91-93. Winter 2000-01. Print.

Savage, Candace. Bird Brains. San Francisco: Sierra Club Books, 1995. Print.